Paper sizing composition with salt of calcium (II) and organic acid, products made thereby, method of using, and method of making

ABSTRACT

A paper sizing composition is provided, which comprises a water-soluble salt of Ca(II) and at least one organic acid; and starch. Methods of making and using the composition, and methods of making and using the recording sheets which include the composition, are disclosed.

BACKGROUND Field of the Invention

The invention relates to compositions and methods of making same for usein papermaking. The invention also relates to methods of making andusing paper products that include the composition.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments are described in association with the accompanyingdrawings, wherein:

FIG. 1 graphically shows the average values of black density obtainedfrom printed recording sheets using several exemplary and comparativecompositions.

FIG. 2 shows black density data obtained from printed recording sheetsusing several exemplary and comparative compositions in tabular form.

FIG. 3 shows black density data obtained from printed recording sheetsusing several exemplary and comparative compositions in columnar form.

FIG. 4 shows color gamut data obtained from printed recording sheetsusing several exemplary and comparative compositions.

FIG. 5 shows average of mean ISO brightness (C) versus average opticalbrightening agent (OBA) pickup on papers sized with various salts.

FIG. 6 shows average of means CIE whiteness (D65) versus average OBApickup on papers sized with exemplary and comparative compositions.

FIG. 7 shows average of mean black density versus average OBA pickup onpapers sized with exemplary and comparative compositions.

FIG. 8 shows average of mean gamut volume versus average OBA pickup onpapers sized with exemplary and comparative compositions.

FIG. 9 shows average color gamut obtained with several printers usingpapers sized with exemplary and comparative compositions.

FIG. 10 shows OD and color gamut data obtained using an HP Officejet Pro8000 printer with papers sized with various exemplary and comparativecompositions.

FIG. 11 shows a summary of OD for papers sized with various exemplaryand comparative compositions.

FIG. 12 shows cyan density obtained using HP Officejet Pro 8000 printerwith papers sized with various exemplary and comparative compositions.

FIG. 13 shows yellow density obtained using HP Officejet Pro 8000printer with papers sized with various exemplary and comparativecompositions.

FIG. 14 shows magenta density obtained using HP Officejet Pro 8000printer with papers sized with various exemplary and comparativecompositions.

FIG. 15 shows black density obtained using HP Officejet Pro 8000 printerwith papers sized with various exemplary and comparative compositions.

FIG. 16 shows color gamut obtained using HP Officejet Pro 8000 printerwith papers sized with various exemplary and comparative compositions.

FIG. 17 shows black OD using drawdown with metal rod and ink and paperssized with various exemplary and comparative compositions.

FIG. 18 graphically shows drawdown black OD with papers sized withvarious exemplary and comparative compositions.

DETAILED DESCRIPTION OF THE SEVERAL EMBODIMENTS

Calcium chloride, CaCl₂, is currently used to enhance inkjet printdensity and dry time. The present inventors have found that calciumchloride undesirably causes corrosion problems in the papermakingmachine, quenches optical brightening agents (OBAs), and is associatedwith low pH, with the result that calcium chloride often is notcompatible with common papermaking chemicals. The present inventors havenow found that these and other problems may be overcome with the severalembodiments described herein.

One embodiment of the present invention desirably achieves enhancedinkjet print density and dry time. Another embodiment desirably reducescorrosion on the papermaking machine. Another embodiment desirablyreduces quenching of optical brightening agents (OBAs) in papermaking.Another embodiment desirably reduces the problems associated with low pHin papermaking. Another embodiment desirably reduces the problems ofcompatibility with common papermaking chemicals. Another embodimentdesirably improves optical properties with lower amounts of opticalbrightening agents. Another embodiment desirably achieves improved inkand printing properties. Another embodiment desirably achieves improvedoptical properties and improved ink and printing properties. Anotherembodiment desirably achieves improved paper machine runnability.Another embodiment desirably achieves improved ink fastness.

One embodiment relates to a paper sizing composition, comprising:

-   -   a water-soluble salt of Ca(II) and at least one organic acid;        and starch.

Another embodiment relates to a method for making a sizing composition,comprising contacting:

-   -   a water-soluble salt of Ca(II) and at least one organic acid;        and starch;        to produce a sizing composition.

Another embodiment relates to a method for making a recording sheet,comprising:

contacting:

a paper substrate comprising a plurality of cellulosic fibers; and

a composition, comprising:

-   -   a water-soluble salt of Ca(II) and at least one organic acid;        and starch;        to produce a recording sheet.

Another embodiment relates to a method, comprising forming an image witha printing apparatus on a surface of a recording sheet, said recordingsheet comprising:

a paper substrate comprising:

a plurality of cellulosic fibers; and

a composition, comprising:

-   -   a water-soluble salt of Ca(II) and at least one organic acid;        and starch.

Another embodiment relates to a recording sheet, comprising:

a paper substrate, comprising:

-   -   a plurality of cellulosic fibers; and    -   a composition, comprising:        -   a water-soluble salt of Ca(II) and at least one organic            acid; and starch.

The organic acid includes any compound having a carboxylic acid groupwhich can disassociate to form a carboxylate group and form a watersoluble salt with Ca(II). In one embodiment, the organic acid has theformula, RCOOH, wherein R is any hydrocarbon. The number of carbons inthe R group is not particularly limited so long as the resulting saltformed with the Ca(II) cation is water soluble. In one embodiment, the Rgroup may have any number of carbon atoms ranging from 1 to 30, whichrange includes all values and subranges therebetween, including 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 23,24, 25, 26, 27, 28, 29, and 30 carbons. The hydrocarbon may be branchedor unbranched, substituted or unsubstituted, saturated or unsaturated,cyclic, heterocyclic, aromatic, or heteroaromatic. One or more of thecarbons in the R group may be optionally substituted with one or moreheteroatoms such as N, S, O, P, and the like. The organic acid may havemore than one carboxylic acid group. The organic acid may bezwitterionic or amphoteric, for example an aminocarboxylic acidcontaining a single C—N bond adjacent (vicinal) to the C—CO₂H bond, suchas EDTA ((HO₂CCH₂)₂NCH₂CH₂N(CH₂CO₂H)₂), DTPA((HO₂CCH₂)₂NCH₂CH₂N(CH₂CO₂H)CH₂CH₂N(CH₂CO₂H)₂), and the like. In oneembodiment, the R group is a saturated or monounsaturated orpolyunsaturaturated C₁-C₅ alkyl, C1-C5 hydroxyalkyl or phenyl.Non-limiting examples of the water soluble salt include calcium acetate,calcium formate, calcium proprionate, calcium lactate, calcium stearate,calcium tartrate, calcium gluconate, calcium citrate, calcium lactategluconate, calcium 2-ethylbutanoate, calcium EDTA, calcium DTPA, calciummagnesium acetate (sometimes referred to as “CMA”); and the like. Theorganic acid may have more than one carboxylic acid group, for example,and may be monovalent, divalent, trivalent, or tetravalent, or of highervalency. The water soluble salt of Ca(II) and the organic acid may be acomplex salt in the sense that two different monovalent organic acidsform the salt with a single Ca(II) ion. In another embodiment, the watersoluble salt of Ca(II) and the organic acid is made with two identicalorganic acids. In another embodiment, the water soluble salt of Ca(II)and the organic acid may be a complex salt in the sense that more thanone Ca(II) cation is present in the salt to counterbalance one or moremultivalent organic acids. In another embodiment, the water soluble saltof Ca(II) and the organic acid may be a complex salt in the sense thatmore than one cation is present in the salt to counterbalance one ormore multivalent organic acids. Mixtures of different water solublesalts of Ca(II) and organic acid are possible.

The amount of water soluble salt of Ca(II) and organic acid present inthe sizing composition is not particularly limited. In one embodiment,it may range from 0.1 to 50% by weight based on the weight of the sizingcomposition. This range includes all values and subranges therebetween,including 0.1, 0.25, 0.5, 0.75, 1, 2.5, 5, 7.5, 10, 15, 20, 25, 30, 35,40, 45, and 50% by weight of the sizing composition.

In one embodiment, the amount of water soluble Ca(II) salt of theorganic acid ranges from about 2 to about 100 lbs Ca(II) salt/ton ofpaper. This range includes all values and subranges therebetween,including about 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 25, 30,40, 50, 60, 70, 80, 90, and 100 lbs Ca(II) salt of organic acid/ton ofpaper.

In one embodiment, the amount of calcium (II) ranges from about 1 toabout 30 lbs calcium (II)/ton of paper. This range includes all valuesand subranges therebetween, including about 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 12, 14, 16, 18, 20, 25, and 30 lbs calcium (II)/ton of paper for 75gsm basis weight paper.

In one embodiment, the water solubility of the calcium (II) salt maysuitably range from slightly or moderately soluble to soluble, measuredas a saturated aqueous solution of the salt at 25° C. In one embodiment,the water solubility at 25° C. may range from 0.002 grams salt/100 ccH₂O and greater. This range includes all values and subrangestherebetween, including about 0.002, 0.003, 0.004, 0.005, 0.007, 0.009,0.01, 0.02, 0.03, 0.05, 0.07, 0.09, 0.1, 0.5, 1, 1.5, 2, 5, 7, 10, 15,20, 25 grams salt/100 cc H₂O and higher. In one embodiment, the watersolubility of the salt ranges from 0.002 to 100 grams salt/100 cc H₂O.

The amount of water soluble Ca(II) salt in contact with the substratecan vary widely. In one embodiment, this amount is at least 0.02 g/m²,although lower or higher amounts can be used. In one embodiment, theamount of water soluble Ca(II) salt is from about 0.02 g/m² to about 4g/m², which ranges includes all values and subranges therebetween,including 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3,0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 2.25, 2.5, 2.75, 3, 3.25, 3.5,3.75, and 4 g/m² or any combination thereof.

The composition may or may not contain CaCl₂. In one embodiment, CaCl₂is not present in the composition.

In one embodiment, the calcium (II) salt is soluble in the amount usedin the sizing formulation. In one embodiment, it is soluble at about pH7 to about pH 9. The sizing medium may be an aqueous solution, emulsion,dispersion, or a latex or colloidal composition, and the term “emulsion”is used herein, as is customary in the art, to mean either a dispersionof the liquid-in-liquid type or of the solid-in-liquid type, as well aslatex or colloidal composition.

The starch is not particularly limited. It may be modified orunmodified. Non-limiting examples of starch may be found in the“Handbook for Pulp and Paper Technologists” by G. A. Smook (1992), AngusWilde Publications, the contents of which are hereby incorporated byreference. Non-limiting examples of modified starches include, forexample, oxidized, cationic, ethylated, hydroethoxylated, etc. Thestarch may come from any source, such as potato or corn. In oneembodiment, the starch source is corn. Mixtures of starches arepossible.

Other non-limiting examples of starches include naturally occurringcarbohydrates synthesized in corn, tapioca, potato, and other plants bypolymerization of dextrose units. All such starches and modified formsthereof such as starch acetates, starch esters, starch ethers, starchphosphates, starch xanthates, anionic starches, cationic starches,oxidized starches, and the like which can be derived by reacting thestarch with a suitable chemical or enzymatic reagent can be used. Ifdesired, starches may be prepared by known techniques or obtained fromcommercial sources. Example of commercial starches include Ethylex 2035from A. E. Staley, PG-280 from Penford Products, oxidized corn starchesfrom ADM, Cargill, and Raisio, and enzyme converted starches such asAmyzet 150 from Amylum. Mixtures are possible.

Other modified starches may be used. Non-limiting examples of a type ofmodified starches include cationic modified or chemically modifiedstarches such as ethylated starches, oxidized starches, and AP andenzyme converted Pearl starches. Chemically modified starches such asethylated starches, oxidized starches, and AP and enzyme converted Pearlstarches are possible. Mixtures are possible.

In one embodiment, the starch is not ethylated starch.

The amount of starch is not particularly limited. In one embodiment, Inone embodiment, it may range from 0.1 to 75% by weight based on theweight of the sizing composition. This range includes all values andsubranges therebetween, including 0.1, 0.25, 0.5, 0.75, 1, 2.5, 5, 7.5,10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, and 75% by weight ofthe sizing composition.

In one embodiment, the amount of starch in the sizing composition mayrange from 5 to 300 lbs/ton. This range includes all values andsubranges therebetween, including 5, 10, 15, 20, 25, 30, 35, 40, 45, 50,75, 100, 125, 150, 175, 200, 250, and 300 lbs/ton.

In one embodiment, the sizing composition is applied in an amount suchthat a dry pickup of 10 to 250 lbs of starch/ton of paper at 12-50%solids for the size press formulation is obtained. The aforementionedrange of starch includes all values and subranges therebetween,including 10, 20, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90,95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 200, and 250lbs/ton.

In one embodiment, lbs/ton is calculated on a paper having a basisweight equal to 75 gsm. It should be readily apparent that the amountsin lbs/ton and moles/ton may vary in a known manner according to thebasis weight of the paper, and the embodiments are not limited to onlypaper having a basis weight of 75 gsm.

In one embodiment, the % solids in the sizing composition may suitablyrange from at least 5-75%. This range includes all values and subrangestherebetween, including 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,18, 19, 20, 21, 22, 23, 24, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, and75% by weight of the sizing composition.

A recording sheet may suitably contain an effective amount of the watersoluble Ca(II) salt and starch in contact with at least one surface ofthe substrate. As used herein, an “effective amount” is an amount whichis sufficient to obtain a good dry time, water fastness, or printingproperty, for example black density, color gamut, and the like. In oneembodiment, the dry pickup of the sizing composition may suitably rangefrom 0.25 to 8 gsm, which range includes all values and subrangestherebetween, for example, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1,2, 3, 4, 5, 6, 7, and 8 gsm.

In one embodiment, the recording sheet comprises 30 to 150 lbs/ton ofstarch and 10 to 50 lbs/ton water soluble salt of Ca(II) and organicacid (3 to 15 lbs/ton of calcium).

The composition may optionally contain one or more optical brighteningagents, sometimes referred to as optical brighteners or OBAs. Typically,the optical brightening agents are fluorescent dyes or pigments thatabsorb ultraviolet radiation and reemit it at a higher wavelengths inthe visible spectrum (blue), thereby effecting a white, brightappearance to the paper sheet when added to the stock furnish.Non-limiting optical brighteners include azoles, biphenyls, coumarins,furans, stilbenes, ionic brighteners, including anionic, cationic, andanionic (neutral) compounds, such as the Eccobrite™ and Eccowhite™compounds available from Eastern Color & Chemical Co. (Providence,R.I.); naphthalimides; pyrazenes; substituted (e.g., sulfonated)stilbenes, such as the Leucophor™ range of optical brighteners availablefrom the Clariant Corporation (Muttenz, Switzerland), and Tinopal™ fromCiba Specialty Chemicals (Basel, Switzerland); salts of such compoundsincluding but not limited to alkali metal salts, alkaline earth metalsalts, transition metal salts, organic salts and ammonium salts of suchbrightening agents; and combinations of one or more of the foregoingagents. Mixtures are possible.

In one embodiment, the optical brighteners are selected from the groupincluding disulfonated, tetrasulfonated, and hexasulfonatedstilbene-based OBAs, and combinations thereof.

The amount of optical brightening agent is not particularly limited. Theoptical brighteners may be added in any amount ranging from 0.1 to 100pounds per 100 pounds of sizing composition. This range includes allvalues and subranges therebetween, including 0.1, 0.25, 0.5, 0.75, 1, 2,3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70,75, 80, 85, 90, 95 and 100 pounds. In another embodiment, the opticalbrightening agent may be added in amounts ranging from about 0.005 toabout 4 weight percent based on the weight of the paper product, such asa recording sheet. This range includes all values and subrangestherebetween, including about 0.005, 0.006, 0.007, 0.008, 0.009, 0.01,0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5,0.6, 0.7, 0.8, 0.9, 1, 2, 3, and 4 weight percent based on the weight ofthe paper product.

In one embodiment, the composition contains the water soluble Ca(II)salt of an organic acid with Ca(II) as the sole cation in the watersoluble Ca(II) salt of the organic acid.

So long as the composition contains the water soluble Ca(II) salt of anorganic acid, the sizing composition may optionally contain one or moreadditional salts. For example, in addition to the water soluble Ca(II)salt of the organic acid, the sizing composition may contain none, orone or more additional salts. For example, the additional salt mayinclude one or more additional water soluble monovalent, divalent, ortetravalent metal salts. Examples of additional monovalent water solublemetal salts include but are not limited to sodium, potassium, and thelike. Examples of additional divalent water soluble metal salts includebut are not limited to compounds containing divalent calcium, magnesium,barium, zinc, or any combination of these. The counter ions (anions) maybe simple or complex and may vary widely. Non-limiting examples of suchmaterials are calcium chloride, magnesium chloride, Mg EDTA, and thelike, and combinations thereof.

In one embodiment, the divalent metal salt may be a mineral or organicacid salt of a divalent cationic metal ion, or a combination thereof. Inone embodiment, the water soluble metal salt may include a halide,nitrate, chlorate, perchlorate, sulfate, acetate, carboxylate,hydroxide, nitrite, or the like, or combinations thereof, of calcium,magnesium, barium, zinc(II), or the like, or combinations thereof. Someexamples of divalent metal salts include, without limitation, sodiumacetate, calcium chloride, magnesium chloride, magnesium bromide,calcium bromide, barium chloride, calcium nitrate, magnesium nitrate,barium nitrate, calcium acetate, magnesium acetate, barium acetate,calcium magnesium acetate, magnesium propionate, barium propionate,calcium nitrite, calcium hydroxide, zinc chloride, zinc acetate, andcombinations thereof. Mixtures or combinations of salts of differentdivalent metals, different anions, or both are possible. The relativeweight of the divalent cationic metal ion in the divalent metal salt maybe maximized, if desired, with respect to the anion in the salt toprovide enhanced properties based on the total weight of applied salt.

The composition may optionally include one or more co-crystalline saltof an inorganic acid, organic acid, organometallic compound, or othermetal complex (other than metal oxides) in which a ligand is bound to ametal ion by a chemical bond, such as a covalent bond, ionic bond,coordination covalent bond, metallic bond, aromatic bond or bent bond.In one embodiment, the co-crystalline salt is soluble or dispersible inwater or other aqueous solvent. Examples of suitable metal cationsinclude, but are not limited to, potassium, sodium, lithium, aluminum,calcium, magnesium, zinc, iron, strontium, barium, nickel, copper,scandium, gallium, indium, titanium, zirconium, tin and lead. In oneembodiment, co-crystalline compounds comprising magnesium, aluminum,zirconium, calcium and zinc cations may be suitable when a colorlesscomposition is desired. In one embodiment, the co-crystalline saltcontains one or more polyvalent metal cations. Mixtures ofco-crystalline salts are possible.

Non-limiting examples of multi-cation co-crystalline salts includepotassium sodium tartrate, potassium sodium bromlite; potassiumdihydrogen citrate; lithium potassium hydrogen citrate monohydrate;tamarugite (NaAl(SO₄)_(x).6H₂O), barium silicon iodide (Ba₃SiI₂);potassium tetrachloroaluminate (AlKCl₄); lithium tetrachloroaluminate(AlLiCl₄); sodium tetrachloroaluminate (AlNaCl₄); cesiumtetrachloroaluminate (AlCeCl₄); aluminum hexafluoroaluminate; postassiumaluminum sulfate dodecahydrate; potassium tetrafluorobotate (BF₄K);lithium tetrafluorobotate; sodium tetrafluorobotate; calciumtetrafluoroborate hydrate (B₂CaF₈); tin tetrafluoroborate (B₂SnF₈);titanium chloride-aluminum chloride (AlCi₂Ti₃); aluminum cesium sulfatedodecahydrate (AlCsO₈S₂.12H₂O); magnesium aluminum hydrotalcites, andcalcium magnesium acetate; salts of alkali sulfates having the generalformula M⁺ ₂SO₄.M³⁺ ₂(SO₄)₃.24H₂O, wherein M⁺ is an alkali metal (e.g.,lithium, sodium, potassium, rubidium, or cesium) or ammonium ion (NH⁴⁺),and M³⁺ is a trivalent metal ion (e.g., aluminum, chromium, or iron(III)). Mixtures are possible.

Multi-anion co-crystalline salts may also be used. They include, but arenot limited to, zinc chloride co-crystalline salts such as4-phenoxydiazobenzene zinc chloride and2,5-dimethoxy-4-tolylmercaptodiazobenzene zinc chloride; and magnesiumnitrate co-crystalline salts such as triacetatohexaaquodimagnesiumnitrate. Mixtures are possible.

The composition can be added to bleached pulp or paper product at anypoint in the paper manufacturing process. Some examples of additionpoints include, but are not limited to (a) to the pulp slurry in thelatency chest; (b) to the pulp during or after the bleaching stage in astorage, blending or transfer chest; (c) before the final debleachingstage where the pH is alkaline; (d) to pulp after bleaching, washing anddewatering followed by cylinder or flash drying; (e) before or after thecleaners; (f) before or after the fan pump to the paper machine headbox;(g) to the paper machine white water; (h) sprayed or showered onto themoving wet web after head box forming but before wet press; (i) to thesilo or save all; (j) in the press section using, for example, a sizepress, coater or spray bar; (k) in the drying section using, forexample, a size press, coater or spray bar; (l) on the calender using awafer box; (m) on paper in an off-machine coater or size press; and/or(n) in the curl control unit. Combinations are possible.

The precise location where the composition is added will depend on thespecific equipment involved, the exact process conditions being used andthe like. In some cases, one or more sizing compositions, having thesame or different composition—so long as it contains the water solubleCa(II) salt of the organic acid and starch—may be added at one or morelocations for optimal effectiveness.

Application can be by any means conventionally used in papermakingprocesses, including by “split-feeding” whereby one or more of the watersoluble salts of Ca(II) and organic acid and/or starch is/are applied atone point in the papermaking process, for example on pulp or a wet sheet(before the dryers) and the remaining portion of one or more of thewater soluble salts of Ca(II) and organic acid and/or starch is/areadded at a subsequent point, for example in the size press.

In one embodiment, the starch can be added to a bleached pulp or paperproduct before, after, or simultaneously with the water soluble Ca(II)salt. The optical brightener may also be formulated with the watersoluble Ca(II) salt, starch, or both.

In one embodiment, the sizing composition may be applied in the sizepress.

The sizing composition may be applied to, mixed with, or contacted witha paper substrate to produce a recording sheet. The paper substratesuitably comprises a plurality of cellulosic fibers. The type ofcellulosic fiber is not critical, and any such fiber known or suitablefor use in paper making can be used. For example, the substrate can madefrom pulp fibers derived from hardwood trees, softwood trees, or acombination of hardwood and softwood trees. The fibers may be preparedfor use in a papermaking furnish by one or more known or suitabledigestion, refining, and/or bleaching operations such as, for example,known mechanical, thermomechanical, chemical and/or semichemical pulpingand/or other well known pulping processes. The term, “hardwood pulps” asused herein may include fibrous pulp derived from the woody substance ofdeciduous trees (angiosperms) such as birch, oak, beech, maple, andeucalyptus. The term, “softwood pulps” as used herein may includefibrous pulps derived from the woody substance of coniferous trees(gymnosperms) such as varieties of fir, spruce, and pine, as for exampleloblolly pine, slash pine, Colorado spruce, balsam fir and Douglas fir.In some embodiments, at least a portion of the pulp fibers may beprovided from non-woody herbaceous plants including, but not limited to,kenaf, hemp, jute, flax, sisal, or abaca, although legal restrictionsand other considerations may make the utilization of hemp and otherfiber sources impractical or impossible. Either bleached or unbleachedpulp fiber may be utilized. Recycled pulp fibers are also suitable foruse.

The paper substrate may suitably contain from 1 to 99 wt % of cellulosicfibers based upon the total weight of the substrate. In one embodiment,the paper substrate may contain from 5 to 95 wt % of cellulosic fibersbased upon the total weight of the substrate. These ranges include anyand all values and subranges therebetween, for example, 1, 5, 10, 15,20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 and 99 wt%.

The paper substrate may optionally contain from 1 to 100 wt % cellulosicfibers originating from softwood species based upon the total amount ofcellulosic fibers in the paper substrate. In one embodiment, the papersubstrate may contain 10 to 60 wt % cellulosic fibers originating fromsoftwood species based upon the total amount of cellulosic fibers in thepaper substrate. These ranges include 1, 2, 5, 10, 15, 20, 25, 30, 35,40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, and 100 wt % and any andall ranges and subranges therein, based upon the total amount ofcellulosic fibers in the paper substrate.

In one embodiment, the paper substrate may alternatively oroverlappingly contain from 0.01 to 99 wt % fibers from softwood species,based on the total weight of the paper substrate. In another embodiment,the paper substrate may contain from 10 to 60 wt % fibers from softwoodspecies based upon the total weight of the paper substrate. These rangesinclude any and all values and subranges therein. For example, the papersubstrate may contain not more than 0.01, 0.05, 0.1, 0.2, 0.5, 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65,70, 75, 80, 85, 90, 95 and 99 wt % softwood based upon the total weightof the paper substrate.

All or part of the softwood fibers may optionally originate fromsoftwood species having a Canadian Standard Freeness (CSF) of from 300to 750. In one embodiment, the paper substrate contains fibers from asoftwood species having a CSF from 400 to 550. These ranges include anyand all values and subranges therebetwen, for example, 300, 310, 320,330, 340, 350, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450, 460,470, 480, 490, 500, 510, 520, 530, 540, 550, 560, 570, 580, 590, 600,610, 620, 630, 640, 650, 660, 670, 680, 690, 700, 710, 720, 730, 740,and 750 CSF. Canadian Standard Freeness is as measured by TAPPI T-227standard test.

The paper substrate may optionally contain from 1 to 100 wt % cellulosicfibers originating from hardwood species based upon the total amount ofcellulosic fibers in the paper substrate. In one embodiment, the papersubstrate may contain from 30 to 90 wt % cellulosic fibers originatingfrom hardwood species, based upon the total amount of cellulosic fibersin the paper substrate. These ranges include 1, 2, 5, 10, 15, 20, 25,30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, and 100 wt %,and any and all values and subranges therein, based upon the totalamount of cellulosic fibers in the paper substrate.

In one embodiment, the paper substrate may alternatively oroverlappingly contain from 0.01 to 99 wt % fibers from hardwood species,based upon the total weight of the paper substrate. In anotherembodiment, the paper substrate may alternatively or overlappinglycontain from 60 to 90 wt % fibers from hardwood species, based upon thetotal weight of the paper substrate. These ranges include any and allvalues and subranges therebetween, including not more than 0.01, 0.05,0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 25, 30, 35,40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 99 and 99 wt %, basedupon the total weight of the paper substrate.

All or part of the hardwood fibers may optionally originate fromhardwood species having a Canadian Standard Freeness of from 300 to 750.In one embodiment, the paper substrate may contain fibers from hardwoodspecies having CSF values of from 400 to 550. These ranges include 300,310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 410, 420, 430, 440,450, 460, 470, 480, 490, 500, 510, 520, 530, 540, 550, 560, 570, 580,590, 600, 610, 620, 630, 640, 650, 660, 670, 680, 690, 700, 710, 720,730, 740, and 750 CSF, and any and all ranges and subranges therein.

The paper substrate may optionally contain less refined fibers, forexample, less refined softwood fibers, less refined hardwood fibers, orboth. Combinations of less refined and more refined fibers are possible.In one embodiment, the paper substrate contains fibers that are at least2% less refined than that of fibers used in conventional papersubstrates. This range includes all values and subranges therebetween,including at least 2, 5, 10, 15, and 20%. For example, if a conventionalpaper contains fibers, softwood and/or hardwood, having a CanadianStandard Freeness of 350, then, in one embodiment, the paper substratemay contain fibers having a CSF of 385 (i.e. refined 10% less thanconventional) and still perform similar to, if not better than, theconventional paper. Examples of some reductions in refining of hardwoodand/or softwood fibers include, but are not limited to: 1) from 350 toat least 385 CSF; 2) from 350 to at least 400 CSF; 3) from 400 to atleast 450 CSF; and 4) from 450 to at least 500 CSF. In some embodiments,the reduction in fiber refinement may be at least 2, 3, 4, 5, 6, 7, 8,9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, and 25% reduction inrefining compared to those fibers in conventional paper substrates.

When the paper substrate contains both hardwood fibers and softwoodfibers, the hardwood/softwood fiber weight ratio may optionally rangefrom 0.001 to 1000. In one embodiment, the hardwood/softwood ratio mayrange from 90/10 to 30/60. These ranges include all values and subrangestherebetween, including 0.001, 0.002, 0.005, 0.01, 0.02, 0.05, 0.1, 0.2,0.5, 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75,80, 85, 90, 95, 100, 200, 300, 400, 500, 600, 700, 800, 900, and 1000.

The softwood fibers, hardwood fibers, or both may be optionally modifiedby physical and/or chemical processes. Examples of physical processesinclude, but are not limited to, electromagnetic and mechanicalprocesses. Examples of electrical modifications include, but are notlimited to, processes involving contacting the fibers with anelectromagnetic energy source such as light and/or electrical current.Examples of mechanical modifications include, but are not limited to,processes involving contacting an inanimate object with the fibers.Examples of such inanimate objects include those with sharp and/or dulledges. Such processes also involve, for example, cutting, kneading,pounding, impaling, and the like, and combinations thereof.

Non-limiting examples of chemical modifications include conventionalchemical fiber processes such as crosslinking and/or precipitation ofcomplexes thereon. Other examples of suitable modifications of fibersinclude those found in U.S. Pat. Nos. 6,592,717, 6,592,712, 6,582,557,6,579,415, 6,579,414, 6,506,282, 6,471,824, 6,361,651, 6,146,494,H1,704, 5,731,080, 5,698,688, 5,698,074, 5,667,637, 5,662,773,5,531,728, 5,443,899, 5,360,420, 5,266,250, 5,209,953, 5,160,789,5,049,235, 4,986,882, 4,496,427, 4,431,481, 4,174,417, 4,166,894,4,075,136, and 4,022,965, the entire contents of each of which arehereby incorporated, independently, by reference. Still other examplesof suitable modifications of fibers may be found in U.S. ApplicationNos. 60/654,712, filed Feb. 19, 2005, and Ser. No. 11/358,543, filedFeb. 21, 2006, which may include the further addition of opticalbrighteners (i.e. OBAs) as discussed therein, the entire contents ofeach of which are hereby incorporated, independently, by reference.

The paper substrate may optionally include “fines.” “Fines” fibers aretypically those fibers with average lengths of not more than about 100μm. Sources of “fines” may be found in SaveAll fibers, recirculatedstreams, reject streams, waste fiber streams, and combinations thereof.The amount of “fines” present in the paper substrate can be modified,for example, by tailoring the rate at which streams are added to thepaper making process. In one embodiment, the average lengths of thefines are not more than about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55,60, 65, 70, 75, 80, 85, 90, 95, and 100 μm, including any and all rangesand subranges therein.

If used, the “fines” fibers may be present in the paper substratetogether with hardwood fibers, softwood fibers, or both hardwood andsoftwood fibers.

The paper substrate may optionally contain from 0.01 to 100 wt % fines,based on the total weight of the paper substrate. In one embodiment, thepaper substrate may contain from 0.01 to 50 wt % fines, based upon thetotal weight of the substrate. These ranges include all values andsubranges therebetween, including not more than 0.01, 0.05, 0.1, 0.2,0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 25, 30, 35, 40, 45, 50,55, 60, 65, 70, 75, 80, 85, 90, 95 and 100 wt % fines, based upon thetotal weight of the paper substrate.

In one embodiment, the paper substrate may alternatively oroverlappingly contain from 0.01 to 100 wt % fines, based upon the totalweight of the fibers in the paper substrate. This range includes allvalues and subranges therebetween, including not more than 0.01, 0.05,0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 25, 30, 35,40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 and 100 wt % fines, basedupon the total weight of the fibers in by the paper substrate.

The composition and/or recording sheet may optionally contain one ormore additional sizing agents. The additional sizing agent is notparticularly limited, and any conventional papermaking sizing agent maybe used. The additional sizing agent may be nonreactive, reactive, or acombination of nonreactive and reactive. The additional sizing agentmay, optionally and if desired, impart a moisture or water-resistance invarying degrees to the paper substrate. Non-limiting examples ofadditional sizing agents can be found in the “Handbook for Pulp andPaper Technologists” by G. A. Smook (1992), Angus Wilde Publications,already incorporated by reference. Non-limiting examples os additionalsizing agents include alkyl ketene dimer (AKD), alkenyl ketene dimer(ALKD), alkenyl succinic anhydride (ASA), ASA/ALKD, styrene acrylicemulsion (SAE) polyvinyl alcohol (PVOH), polyvinylamine, alginate,carboxymethyl cellulose, etc.

The additional sizing agent may include nonreactive sizing agents, suchas are known in the art. Examples include, without limitation, a polymeremulsion, a cationic polymer emulsion, an amphoteric polymer emulsion,polymer emulsion wherein at least one monomer is selected from the groupincluding styrene, α-methylstyrene, acrylate with an ester substituentwith 1 to 13 carbon atoms, methacrylate having an ester substituent with1 to 13 carbon atoms, acrylonitrile, methacrylonitrile, vinyl acetate,ethylene and butadiene; and optionally including acrylic acid,methacrylic acid, maleic anhydride, esters of maleic anhydride ormixtures thereof, with an acid number less than about 80, and mixturesthereof, BASOPLAST® 335D nonreactive polymeric surface size emulsionfrom BASF Corporation (Mt. Olive, N.J.), FLEXBOND® 325 emulsion of acopolymer of vinyl acetate and butyl acrylate from Air Products andChemicals, Inc. (Trexlertown, Pa.), and PENTAPRINT® nonreactive sizingagents, and the like, and combinations thereof.

Other additional sizing agents, for example, non-reactive dispersedrosin sizing agents may be optionally used. Dispersed rosin sizingagents are well known. Non-limiting examples of rosin sizing agents aredisclosed in, for example, U.S. Pat. Nos. 3,966,654 and 4,263,182, theentire contents of each of which are hereby incorporated by reference.The rosin may be any modified or unmodified, dispersible or emulsifiablerosin suitable for sizing paper, including unfortified rosin, fortifiedrosin and extended rosin, as well as rosin esters, and mixtures andblends thereof. The rosin in dispersed form is not particularly limited,and any of the commercially available types of rosin, such as woodrosin, gum rosin, tall oil rosin, and mixtures of any two or more, intheir crude or refined state, may be used. In one embodiment, tall oilrosin and gum rosin are used. Partially hydrogenated rosins andpolymerized rosins, as well as rosins that have been treated to inhibitcrystallization, such as by heat treatment or reaction withformaldehyde, may also be employed.

Mixtures of Additional Sizing Agents are Possible.

The composition may be suitably used as an internal sizing, an externalsizing, or both. The internal and external sizing compositions may havethe same or different compositions. When used as both internal andexternal sizing, the sizing compositions may be present in any weightratio and may be the same and/or different. Alternatively, the recordingsheet may use different internal or external sizing compositions,wherein only one sizing contains the water soluble Ca(II) salt of theorganic acid and starch, and the other sizing does not contain the watersoluble Ca(II) salt of the organic acid or starch. In one embodiment,the weight ratio of surface sizing to internal sizing is from 50/50 to100/0 or from 75/25 to 100/0 surface/internal sizing. In anotherembodiment, the weight ratio of internal sizing to external sizing isfrom 50/50 to 100/0 or from 75/25 to 100/0 internal/surface sizing Theseranges include 50/50, 55/45, 60/40, 65/35, 70/30, 75/25, 80/20, 85/15,90/10, 95/5 and 100/0, including any and all ranges and subrangestherein.

In one embodiment, the sizing composition may be applied to one or bothsides of a paper substrate.

The amount of water soluble metal Ca(II) salt of the organic acid andstarch in and/or on the substrate is not particularly limited.

The sizing composition may also include one or more optional additivessuch as binders, pigments, thickeners, defoamers, surfactants, slipagents, dispersants, optical brighteners, dyes, and preservatives, whichare well-known. Examples of pigments include, but are not limited to,clay, calcium carbonate, calcium sulfate hemihydrate, and calciumsulfate dehydrate, chalk, GCC, PCC, and the like. In one embodiment, thepigment is calcium carbonate, for example precipitated calciumcarbonate. Examples of binders include, but are not limited to,polyvinyl alcohol, Amres (a Kymene type), Bayer Parez, polychlorideemulsion, polyacrylamide, modified polyacrylamide, polyol, polyolcarbonyl adduct, ethanedial/polyol condensate, polyimide,epichlorohydrin, glyoxal, glyoxal urea, ethanedial, aliphaticpolyisocyanate, isocyanate, 1,6 hexamethylene diisocyanate,diisocyanate, polyisocyanate, polyester, polyester resin, polyacrylate,polyacrylate resin, acrylate, and methacrylate. Other optional additivesinclude, but are not limited to silicas such as colloids and/or sols.Examples of silicas include, but are not limited to, sodium silicateand/or borosilicates. Other additives which may be used include one ormore solvents such as, for example, water. Combinations of additives arepossible.

It may be advantageous that a majority of the total amount of sizingcomposition is located at or near the outside surface or surfaces (inthe case of the sizing applied to both surfaces) of the paper substrate.In one embodiment, the paper substrate contains the sizing compositionsuch that the substrate and the sizing composition cooperate to form anI-beam structure. I-beam structures are discussed, for example, U.S.Patent Publication No. 2004/0065423, published Apr. 8, 2004, and in theUS Provisional Application filed by International Paper and havingdocket number COM-042546-P1, the entire contents of each of which arehereby incorporated independently by reference. In this regard, it isnot required that the sizing composition interpenetrates with thecellulosic fibers of the substrate. However, if the sizing or coatinglayer and the cellulose fibers interpenetrate, it will create a papersubstrate having an interpenetration layer, which is within the ambit ofthe present invention.

In one embodiment, the interpenetration layer of the paper substrate maydefine a region in which at least the sizing composition penetrates intoand is among the cellulose fibers. The interpenetration layer may befrom 1 to 99% of the entire cross section of at least a portion of thepaper substrate, including 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50,55, 60, 65, 70, 75, 80, 85, 90, 95, and 99% of the paper substrate,including any and all ranges and subranges therein. Such an embodimentmay be made, for example, when the sizing composition is added to thecellulose fibers prior to a coating method and may be combined with asubsequent coating method if required. Addition points may be at thesize press, for example.

In one embodiment, the cross-sectional thickness of the interpenetrationlayer may be minimized. Alternatively, or additionally, theconcentration of the sizing composition increases as one moves (in thez-direction normal to the plane of the substrate) from the interiorportion towards the surface of the paper substrate. Therefore, theamount of sizing composition present towards the top and/or bottom outersurfaces of the substrate may be greater than the amount of sizingcomposition present towards the inner middle of paper substrate.Alternatively, a majority percentage of the sizing composition may belocated at a distance from the outside surface of the substrate that isequal to or less than 25%, more preferably 10%, of the total thicknessof the substrate. This aspect may also be known as the Q_(total), whichis measured by known methodologies outlined, for example, in U.S. PatentPublication No. 2008/0035292, published Feb. 14, 2008, the entirecontents of which are hereby incorporated by reference. If Q_(total) isequal to 0.5, then the sizing composition interpenetrates and isapproximately evenly distributed throughout the paper substrate. IfQ_(total) is greater than 0.5, then there is more sizing towards thecentral portion (measured by the z-direction normal to the plane of thesubstrate) of the paper substrate than towards the paper substrate'ssurface or surfaces. If Q_(total) is less than 0.5, then there is lesssizing towards the central portion of the paper substrate than towardsthe paper substrate's surface or surfaces. In light of the above, thepaper substrate may have a Q_(total) that is less than 0.5, or from 0 toless than 0.5. This range includes 0, 0.001, 0.002, 0.005, 0.01, 0.02,0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, and 0.49, includingany and all ranges and subranges therein.

As noted above, the determination of Q may be suitably carried outaccording to the procedures in U.S. Patent Publication 2008/0035292,published Feb. 14, 2008.

The paper substrate may be pressed in a press section containing one ormore nips. Any pressing means commonly known in the art of papermakingmay be utilized. The nips may be, but are not limited to, single felted,double felted, roll, and extended nip in the presses.

The paper substrate and/or recording sheet may be dried in a dryingsection. Any drying means commonly known in the art of papermaking maybe utilized. The drying section may include and contain a drying can,cylinder drying, Condebelt drying, IR, or other drying means andmechanisms known in the art. The paper substrate may be dried so as tocontain any selected amount of water. In one embodiment, the substrateis dried to contain less than or equal to 10% water.

The paper substrate and/or recording sheet may be calendered by anycommonly known calendaring means in the art of papermaking, for example,wet stack calendering, dry stack calendering, steel nip calendaring, hotsoft calendaring or extended nip calendering, etc.

The paper substrate and/or recording sheet may be microfinishedaccording to any process commonly known in the art of papermaking.Microfinishing typically involves frictional processes to finishsurfaces of the paper substrate. The paper substrate may bemicrofinished with or without a calendering applied theretoconsecutively and/or simultaneously.

In one embodiment, the paper substrate and/or recording sheet may befurther coated by any conventional coating layer application means,including impregnation means. One method of applying the coating layeris with an in-line coating process with one or more stations. Thecoating stations may be any of known coating means commonly known in theart of papermaking including, for example, brush, rod, air knife, spray,curtain, blade, transfer roll, reverse roll, and/or cast coating means,as well as any combination of the same.

The recording sheet may optionally contain from 0.001 to 20 wt % ofoptional additives based on the total weight of the substrate,preferably from 0.01 to 10 wt %, most preferably 0.1 to 5.0 wt %, ofeach of at least one of the optional additives. This range includes0.001, 0.002, 0.005, 0.006, 0.008, 0.01, 0.02, 0.03, 0.04, 0.05, 0.1,0.2, 0.4, 0.5, 0.6, 0,7, 0.8, 0.9, 1, 2, 4, 5, 6, 8, 10, 12, 14, 15, 16,18, and 20 wt % based on the total weight of the substrate, includingany and all ranges and subranges therein.

Other conventional additives that may be present include, but are notlimited to, one or more wet strength resins, internal sizes, drystrength resins, alum, fillers, pigments and dyes. The substrate mayinclude bulking agents such as expandable microspheres, pulp fibers,and/or diamide salts. Mixtures are possible.

If desired, one or more reducing agents may be optionally added toenhance the effect of the optical brighteners. Some examples of reducingagents are discussed in U.S. Patent Application Publication2007/0062653, incorporated herein by reference in its entirety. Ifutilized, one measure of an effective amount of reducing agent added tobleached pulp or paper product is that which enhances the brightness andresistance to thermal yellowing of the pulp or paper compared to pulp orpaper which is not treated with the reducing agents. Methods fordetermining brightness and resistance to thermal yellowing are known.

Paper substrates suitable for use herein may have any basis weight. Itmay have either a high or low basis weight, including basis weights ofat least 10 lbs/3000 square foot, from 20 to 500 lbs/3000 square foot,or from 40 to 325 lbs/3000 square foot. The basis weight may be at least10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 125, 150, 175, 200, 225, 250,275, 300, 325, 350, 375, 400, 425, 450, 475, and 500 lbs/3000 squarefeet, including any and all ranges and subranges therein.

The recording sheet may be suitably printed by generating images on asurface of the recording sheet using conventional printing processes andapparatus as for example laser, inkjet, offset and flexo printingprocesses and apparatus. In this method, the recording sheet isincorporated into a printing apparatus; and an image is formed on asurface of the sheet. The recording sheet may be printed with inkjetprinting processes and apparatus such as, for example, desk top inkjetprinting and high speed commercial inkjet printing. In one embodiment,an inkjet printing process is contemplated wherein an aqueous recordingliquid is applied to the recording sheet in an image wise pattern. Inanother embodiment, an inkjet printing process is contemplated whichincludes (1) incorporating into an inkjet printing apparatus containingan aqueous ink the recording sheet, and (2) causing droplets of the inkto be ejected in an image wise pattern onto the recording sheet, therebygenerating one or more images on the recording sheet. Inkjet printingprocesses are well known and are described in, for example, U.S. Pat.No. 4,601,777, U.S. Pat. No. 4,251,824, U.S. Pat. No. 4,410,899, U.S.Pat. No. 4,412,224, and U.S. Pat. No. 4,532,530. In one embodiment, theinkjet printing apparatus employs a thermal inkjet process wherein theink in the nozzles is selectively heated in an imagewise pattern,thereby causing droplets of the ink to be ejected onto the recordingsheet in imagewise pattern. The recording sheet can also be used in anyother printing or imaging process, such as printing with pen plotters,imaging with color laser printers or copiers, handwriting with ink pens,offset printing processes, or the like, provided that the toner or inkemployed to form the image is compatible with the recording sheet. Thedetermination of such compatibility is easily carried out given theteachings herein combined with the ordinary skill of one knowledgeablein the printing art.

The recording sheet may be printed if desired with any inkjet printerusing pigmented inks. Pigmented inkjet inks are well known in the art,and typically contain a liquid vehicle, pigment colorants, andadditional components including one or more dyes, humectants,detergents, polymers, buffers, preservatives, and other components. Apigment or any number of pigment blends may be provided in the inkjetink formulation to impart color to the resulting ink. The pigment may beany number of desired pigments dispersed throughout the resulting inkjetink. The pigmented inkjet inks may contain any suitable organic orinorganic pigment particles, including black pigments, white pigments,cyan pigments, magenta pigments, yellow pigments, and the like. Examplesof suitable inorganic pigments are titanium oxide, cobalt blue(CoO—Al₂O₃), chrome yellow (PbCrO₄), and iron oxide. Suitable organicpigments include, for example, carbon black, azo pigments includingdiazo pigments and monoazo pigments, polycyclic pigments {e.g.,phthalocyanine pigments such as phthalocyanine blues and phthalocyaninegreens, perylene pigments, perynone pigments, anthraquinone pigments,quinacridone pigments, dioxazine pigments, thioindigo pigments,isoindolinone pigments, pyranthrone pigments, and quinophthalonepigments), insoluble dye chelates {e.g., basic dye type chelates andacidic dye type chelate), nitropigments, nitroso pigments, anthanthronepigments such as PR168, and the like. Representative examples ofphthalocyanine blues and greens include copper phthalocyanine blue,copper phthalocyanine green and derivatives thereof (Pigment Blue 15 andPigment Green 36). Representative examples of quinacridones includePigment Orange 48, Pigment Orange 49, Pigment Red 122, Pigment Red 192,Pigment Red 202, Pigment Red 206, Pigment Red 207, Pigment Red 209,Pigment Violet 19 and Pigment Violet 42. Representative examples ofanthraquinones include Pigment Red 43, Pigment Red 194 (Perinone Red),Pigment Red 177, Pigment Red 216 (Brominated Pyranthrone Red) andPigment Red 226 (Pyranthrone Red). Representative examples of perylenesinclude Pigment Red 123 (Vermillion), Pigment Red 149 (Scarlet), PigmentRed 179 (Maroon), Pigment Red 190 (Red), Pigment Red 189 (Yellow ShadeRed) and Pigment Red 224. Representative examples of thioindigoidsinclude Pigment Red 86, Pigment Red 87, Pigment Red 88, Pigment Red 181,Pigment Red 198, Pigment Violet 36, and Pigment Violet 38.Representative examples of heterocyclic yellows include Pigment Yellow1, Pigment Yellow 3, Pigment Yellow 12, Pigment Yellow 13, PigmentYellow 14, Pigment Yellow 17, Pigment Yellow 65, Pigment Yellow 73,Pigment Yellow 74, Pigment Yellow 90, Pigment Yellow 110, Pigment Yellow1 17, Pigment Yellow 120, Pigment Yellow 128, Pigment Yellow 138,Pigment Yellow 150, Pigment Yellow 151, Pigment Yellow 155, and PigmentYellow 213. Such pigments are commercially available in either powder orpress cake form from a number of sources including, BASF Corporation,Engelhard Corporation and Sun Chemical Corporation.

Non-limiting examples of black pigments include carbon black, graphite,vitreous carbon, charcoal, and combinations thereof. Such carbonpigments are commercially available from such vendors as CabotCorporation, Columbian Chemicals Company, Degussa AG, and E.I. DuPont deNemours and Company. Suitable carbon black pigments include, but are notlimited to, Cabot pigments such as MONARCH 1400, MONARCH 1300, MONARCH 1100, MONARCH 1000, MONARCH 900, MONARCH 880, MONARCH 800, MONARCH 700,CAB-O-JET 200, CAB-O-JET 300, REGAL, BLACK PEARLS, ELFTEX, MOGUL, andVULCAN pigments; Columbian pigments such as RAVEN 7000, RAVEN 5750,RAVEN 5250, RAVEN 5000, and RAVEN 3500; Degussa pigments such as ColorBlack FW 200, RAVEN FW 2, RAVEN FW 2V, RAVEN FW 1, RAVEN FW 18, RAVENS160, RAVEN FW S170, Special Black 6, Special Black 5, Special Black 4A,Special Black 4, PRINTEX U, PRINTEX 140U, PRINTEX V, and PRINTEX 140V;and TIPURE R-101 available from Dupont. The above list of pigmentsincludes unmodified pigment particulates, small molecule attachedpigment particulates, and polymer-dispersed pigment particulates.Alternatively, almost any commercially available carbon pigment may beused, as long as it provides acceptable optical density and printcharacteristics.

Similarly, a wide variety of colored pigments may be suitably used, andcan be blue, brown, cyan, green, white, violet, magenta, red, orange,yellow, and mixtures thereof. Non limiting examples of suitable colorpigments are CABO-JET 250C, CABO-JET 260M, and CABO-JET 270Y (CabotCorp.); PALIOGEN Orange, PALIOGEN Orange 3040, PALIOGEN Blue L 6470,PALIOGEN Violet 5100, PALIOGEN Violet 5890, PALIOGEN Yellow 1520,PALIOGEN Yellow 1560, PALIOGEN Red 3871K, PALIOGEN Red 3340, HELIOGENBlue L 6901F, HELIOGEN Blue NBD 7010, HELIOGEN Blue K 7090, HELIOGENBlue L 7101F, HELIOGEN Blue L6900, L7020, HELIOGEN Blue D6840, HELIOGENBlue D7080, HELIOGEN Green L8730, HELIOGEN Green K 8683, and HELIOGENGreen L 9140 (BASF Corp); CHROMOPHTAL Yellow 3G, CHROMOPHTAL Yellow GR,CHROMOPHTAL Yellow 8G, IGRAZIN Yellow SGT, IGRALITE Rubine 4BL, IGRALITEBlue BCA, MONASTRAL Magenta, MONASTRAL Scarlet, MONASTRAL Violet R,MONASTRAL Red B, and MONASTRAL Violet Maroon B (Ciba-Geigy Corp.);DALAMAR Yellow YT-858-D and HEUCOPHTHAL Blue G XBT-583D (Heubach Group);Permanent Yellow GR, Permanent Yellow G, Permanent Yellow DHG, PermanentYellow NCG-71, Permanent Yellow GG, Hansa Yellow RA, Hansa BrilliantYellow 5GX-O₂, Hansa Yellow-X, NOVOPERM Yellow HR, NOVOPERM Yellow FGL,Hansa Brilliant Yellow IOGX, Permanent Yellow G3R-01, HOSTAPERM YellowH4G, HOSTAPERM Yellow H3G, HOSTAPERM Orange GR, HOSTAPERM Scarlet GO,HOSTAPERM Pink E, Permanent Rubine F6B, and the HOSTAFINE series(Hoechst Specialty Chemicals); QUINDO Magenta, INDOFAST BrilliantScarlet, QUINDO Red R6700, QUINDO Red R6713, and INDOFAST Violet (MobayCorp.); L74-1357 Yellow, L75-1331 Yellow, and L75-2577 Yellow (SunChemical Corp.). Other examples of color pigments for inkjet inks areNormandy Magenta RD-2400, Permanent Violet VT2645, Argyle Green XP-111-S, Brilliant Green Toner GR 0991, Sudan Blue OS, PV Fast Blue B2GO1,Sudan III, Sudan II, Sudan IV, Sudan Orange G, Sudan Orange 220, OrthoOrange OR2673, Lithol Fast Yellow 0991K, Paliotol Yellow 1840, LumogenYellow D0790, Suco-Gelb L1250, Suco-Yellow D1355, Fanal Pink D4830,Cinquasia Magenta, Lithol Scarlet D3700, Toluidine Red, Scarlet forThermoplast NSD PS PA, E. D. Toluidine Red, Lithol Rubine Toner, LitholScarlet 4440, Bon Red C, Royal Brilliant Red RD-8192, Oracet Pink RF,and Lithol Fast Scarlet L4300 (available, variously, from knowncommercial sources such as Hoechst Celanese Corporation, Paul Uhlich,BASF, American Hoechst, Ciba-Geigy, Aldrich, DuPont, Ugine Kuhlman ofCanada, Dominion Color Company, Magruder, and Matheson).

The inkjet inks may contain one or more distinct type of pigment. In oneembodiment, the mass average diameter of the pigment particles is about10 nm to about 10 μm, and in another embodiment the average diameter isin the range of about 10 nm to about 500 nm, although sizes outsidethese ranges may also be used if the selected pigment can remaindispersed in the ink composition and the pigment particles provideadequate color properties. In one embodiment the pigment is present inan amount in the range of about 1% to about 20% by weight of the inkjetink composition, and in another embodiment is present in an amount inthe range of about 2% to about 6% by weight of the inkjet inkcomposition.

The pigment colorants may include one or more attached dispersant.Dispersants may help to improve dispersion stability, and may also serveto improve bleed control of the ink on the print media. Examples ofsuitable dispersant include, but are not limited to, a carboxylic acid,or a reactive group such as alcohol, amine, anhydride, sulfonic acid,thiol, halotriazine, maleimide, vinyl sulfone, or the like. A widevariety of dispersants for pigmented inkjet inks are known in the art.Such dispersants are broadly classed as polyalkyl glycols, polyalkylimines, aryl dicarboxylic acids such as phthalic acids, isophthalicacids, terephthalic acids, carbohydrates, acrylates, methacrylates,trehalose, and isomers thereof. Generally, the glycol dispersants tendto be stable at neutral and higher pH, while imine dispersants tend tobe stable at lower pH {e.g., about pH 4-6). In some applications, apolyethylene glycol dispersant is attached to the pigment particles inthe ink. Examples of some suitable dispersants include, but are notlimited to, polypropylene glycol, polyethylene imine, polyethyleneglycol, trehalose, and combinations thereof. In some embodiments, thepigment also has a polymer coupled thereto, the polymer beingadditionally coupled to a dispersant, such that the pigment ispolymer-dispersed.

The pigmented inkjet inks may additionally include any suitable vehiclesor additives as are known in the art of preparing inkjet inks. Some ofthese include water, organic co-solvents, dye-based colorants, pHbuffers, viscosity modifiers, antimicrobials, and surfactants.

The term, “about” when referring to a numerical value or range isintended to encompass the values resulting from experimental error thatcan occur when taking measurements.

All of the references, as well as their cited references, cited hereinare hereby incorporated by reference with respect to relative portionsrelated to the subject matter of the present invention and all of itsembodiments.

EXAMPLES

The present invention may be described in further detail with referenceto the following examples. The examples are intended to be illustrative,but the invention is not considered as being limited to the materials,conditions, or process parameters set forth in the examples.

The present inventors have found that the exemplary compositions inaccordance with the several embodiments described herein are morecompatible with papermaking chemicals such as anionic additivesgenerally used at the size press. They have also found that thecompositions quench OBAs less. They have also found that use of thecompositions result in papers having a higher brightness than papersusing CaCl₂ salts. They have also found that for exemplary andcomparative compositions having equal molar amounts of the water solubleCa(II) salts of the organic acid and CaCl₂, the exemplary compositionshave at least the same print density when printed with common desktopinkjet printers, and especially with inkjet printers using pigmentedinks.

FIG. 1 graphically shows the average values of black density usingseveral exemplary, i.e., calcium acetate and calciumproprionate—containing sizing compositions compared to comparativecompositions, i.e., CaCl₂, MgSO₄, and starch-only—compositions. In thefigure, each set of vertical bars represents the average value of blackdensities observed for the various papers printed with the printersnamed on the x-axis. Within each set of vertical bars, the individualbars, when read left to right, correspond to the “Condition” shown inthe legend when read from top to bottom. That is, within each set ofvertical bars, the leftmost bar is for the exemplary “CaAcetate”composition, and the rightmost bar is the comparative “Starch”composition, and so on.

FIG. 2 shows black density data for exemplary and comparativecompositions in tabular form.

FIG. 3 shows black density data for exemplary and comparativecompositions in columnar form.

FIG. 4 shows the color gamut data obtained for exemplary and comparativecompositions when printed with common desktop inkjet printers.

FIG. 5 shows average of mean ISO brightness (C) versus average opticalbrightening agent (OBA) pickup on papers sized with various salts.

FIG. 6 shows average of means CIE whiteness (D65) versus average OBApickup on papers sized with exemplary and comparative compositions.

FIG. 7 shows average of mean black density versus average OBA pickup onpapers sized with exemplary and comparative compositions.

FIG. 8 shows average of mean gamut volume versus average OBA pickup onpapers sized with exemplary and comparative compositions.

FIG. 9 shows average color gamut obtained with several printers usingpapers sized with exemplary and comparative compositions.

FIG. 10 shows OD and color gamut data obtained using an HP Officejet Pro8000 printer with papers sized with various exemplary and comparativecompositions.

FIG. 11 shows a summary of OD for papers sized with various exemplaryand comparative compositions.

FIG. 12 shows cyan density obtained using HP Officejet Pro 8000 printerwith papers sized with various exemplary and comparative compositions.

FIG. 13 shows yellow density obtained using HP Officejet Pro 8000printer with papers sized with various exemplary and comparativecompositions.

FIG. 14 shows magenta density obtained using HP Officejet Pro 8000printer with papers sized with various exemplary and comparativecompositions.

FIG. 15 shows black density obtained using HP Officejet Pro 8000 printerwith papers sized with various exemplary and comparative compositions.

FIG. 16 shows color gamut obtained using HP Officejet Pro 8000 printerwith papers sized with various exemplary and comparative compositions.

FIG. 17 shows black OD using drawdown with metal rod and ink and paperssized with various exemplary and comparative compositions.

FIG. 18 graphically shows drawdown black OD with papers sized withvarious exemplary and comparative compositions.

As used throughout, ranges are used as a short hand for describing eachand every value that is within the range, including all subrangestherein.

Numerous modifications and variations on the present invention arepossible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the accompanying claims, theinvention may be practiced otherwise than as specifically describedherein.

1. A paper sizing composition, comprising: a water-soluble salt ofCa(II) and at least one organic acid; and starch.
 2. The composition ofclaim 1, wherein said salt is present in an amount ranging from 0.1 to50% by weight of the sizing composition.
 3. The composition of claim 1,wherein the salt has a water solubility of greater than 0.002 gramssalt/100 cc of water at 25° C.
 4. The composition of claim 1, whereinthe organic acid has the formula RCOOH, wherein R is a hydrocarbonhaving 1-30 carbon atoms.
 5. The composition of claim 1, wherein theorganic acid is zwitterionic or amphoteric.
 6. The composition of claim1, wherein the salt is a salt having two identical organic acids.
 7. Thecomposition of claim 1, wherein the salt is a complex salt having two ormore different organic acids.
 8. The composition of claim 1, wherein thesalt is calcium acetate, calcium formate, calcium proprionate, calciumlactate, calcium stearate, calcium tartrate, calcium gluconate, calciumcitrate, calcium lactate gluconate, calcium 2-ethylbutanoate, calciumEDTA, calcium DTPA, calcium magnesium acetate, or a mixture thereof. 9.The composition of claim 1, wherein the salt is calcium acetate, calciumformate, calcium proprionate, calcium lactate, calcium stearate, calciumtartrate, calcium gluconate, calcium citrate, calcium lactate gluconate,calcium 2-ethylbutanoate, calcium magnesium acetate, or a mixturethereof.
 10. The composition of claim 1, wherein the starch is presentin an amount ranging from 0.1 to 75% by weight of the sizingcomposition.
 11. The composition of claim 1, which further comprises anoptical brightening agent.
 12. A method for making the composition ofclaim 1, comprising contacting a water-soluble salt of Ca(II) and atleast one organic acid; and starch; to produce the composition ofclaim
 1. 13. A recording sheet, comprising: a paper substrate,comprising: a plurality of cellulosic fibers; and a paper sizingcomposition, comprising: a water-soluble salt of Ca(II) and at least oneorganic acid; and starch.
 14. The recording sheet of claim 13, whereinthe water soluble Ca(II) salt of the organic acid is present in anamount ranging from about 2 to about 100 lbs Ca(II) salt/ton of paper.15. The recording sheet of claim 13, wherein the water soluble Ca(II)salt is present in an amount ranging from about 0.02 g/m² to about 4g/m².
 16. The recording sheet of claim 13, wherein the starch is presentin an amount ranging from about 5 to about 300 lbs/ton.
 17. Therecording sheet of claim 13, wherein the dry pickup of the sizingcomposition ranges from 0.25 to 8 gsm.
 18. The recording sheet of claim13, wherein the sizing composition is an internal sizing.
 19. Therecording sheet of claim 13, wherein the sizing composition is anexternal sizing.
 20. The recording sheet of claim 13, wherein the sizingcomposition is an internal and an external sizing.
 21. The recordingsheet of claim 13, comprising a printed image thereon.
 22. A method formaking a recording sheet, comprising: contacting: a paper substratecomprising a plurality of cellulosic fibers; and a composition,comprising: a water-soluble salt of Ca(II) and at least one organicacid; and starch; to produce a recording sheet.
 23. A method, comprisingforming an image with a printing apparatus on a surface of a recordingsheet, said recording sheet comprising: a paper substrate comprising: aplurality of cellulosic fibers; and a composition, comprising: awater-soluble salt of Ca(II) and at least one organic acid; and starch.